If an optics system requires both the sensing of a target location in a scene by a light-sensitive sensor and the transmission of light to the same location, the boresights of the sensor and the transmitter must be accurately aligned. One possible approach is to use two separate telescopes, one to gather the light for the sensor and the other to direct the output light, and to maintain a fixed parallel boresight arrangement of the two telescopes. However, keeping the boresights of these two separate telescopes aligned and parallel is challenging, particularly in rugged conditions and in adverse environments such as those where the temperature changes significantly so that there are possible thermal expansion differences in the mounting structures of the telescopes. A small angular change between the boresights of the two telescopes translates into a large spatial separation if the target location is a large distance from the position of the optical system.
Another possible approach would be to use an optical system, having a single telescope and a common aperture, for the collection of light for the light sensor and the directing of light from the light source. While this single-telescope approach is appealing, it is difficult to implement where the character of the two optical signals is different. For example, if the light sensor is sensing an image of focused, relatively low-intensity light of a first wavelength, and the light source is afocally transmitting relatively high-intensity light of a second wavelength, such as in the case of a laser rangefinder or laser designator, it is difficult to combine the optics for the two applications into a single telescope.
There is a need for an approach to achieve highly precise aiming of an optical system that performs the dual functions of receiving light for a light sensor and transmitting light from a light source. The present invention fulfills this need, and further provides related advantages.